<!DOCTYPE html>
<title>
  View transitions: Test pagereveal.updateCallbackDone promise is immediately resolved.
</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-2/">
<link rel="author" href="mailto:bokan@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
@view-transition {
  navigation: auto;
}
</style>
<script>
const params = new URLSearchParams(location.search);
const is_initial_page = !params.has('new');

// Ensures microtasks in the current event loop are flushed before control flow
// resumes.
function flushMicrotasks() {
  return new Promise(resolve => resolve());
}

// This test navigates to itself with a changed query parameter. The test
// checks are performed on the navigated-to document.
if (is_initial_page) {
  onload = () => {
    requestAnimationFrame(() => requestAnimationFrame(() => {
      location.replace(location.href + '?new');
    }));
  };
} else {
  promise_test(async () => {
    const ev = await new Promise(
        resolve => addEventListener('pagereveal', e => resolve(e)));

    let updateCallbackDoneResolved = false;
    ev.viewTransition.updateCallbackDone.then(
          () => {updateCallbackDoneResolved = true;});
    await flushMicrotasks();
    assert_true(updateCallbackDoneResolved,
        "updateCallbackDone must be resolved immediately.");
  });
}
</script>
